Biology

1. Biology Properties of Water And Acids/Bases (pH) SB1.d. Explain the impact of water on life processes.

2. Why is water important to humans? • 2/3 of the weight of a cell is WATER! • Look at all the important uses of water in the body…

3. What properties of water make it so useful and important? • Water is polar: a. Has a slight charge on each end. b. One side of water is “+” and the other side is “-” c. This polarity enables water to dissolve many substances

4. What properties of water make it so useful and important? 2. Water is called “Universal solvent”: a. Differences in charges pulls/pushes substances apart so they dissolve

5. What properties of water make it so useful and important? 3.Water is cohesive & adhesive which creates surface tension Cohesive- water molecules stick to each other Adhesive- water molecules stick to other surfaces Surface tension- like a skin of water Ex: how some insects walk on water Surface tension created by cohesiveness of water

6. What properties of water make it so useful and important? 4. Water moves by capillary action • Capillary action- water molecules pull each other up against gravity • This is how trees get water from their roots to their leaves.

7. What properties of water make it so useful and important? 5. Water exhibits evaporative cooling: • removes heat when it evaporates from a surface- ex: sweating • Stores heat- helps maintain earth’s temperature

8. What properties of water make it so useful and important? 6. Water expands during freezing: • ex: rocks broken up by ice to create soil • Also less dense when frozen so floats on liquid water- prevents entire ponds from freezing- which would kill animals in pond

9. So why is water so important to LIFE? • Used in chemical reactions in cells • Helps create soil • Plants use to make food for all • Used to dissolve materials needed in cells • Helps maintain Earth’s temperature

10. What is the pH scale? Measures the concentration of Hydrogen (H+) ions in a solution

11. What is an ACID? 1. release H+ when mixed with water 2. 0-6 on pH scale 3. Sour, corrosive 4. Always have H at front of formula 5. Ex: HCl is hydrochloric acid What is a BASE? 1. release hydroxide (OH-) when mixed with water 2. 8-14 on pH scale 3. Bitter, slippery, usually in cleaners 4. Always have OH at end of formula 5. Ex: NaOH is sodium hydroxide Neutral: H+ ions and OH- ions are equal so it is neutral. They are 7 on pH scale.

12. What’s the pH scale got to do with Biology? • Chemical reactions in cells release and absorb hydrogen- this can change pH. • If pH levels in body are not maintained, electrical chemistry in body doesn’t work- can lead to sickness.

13. What is a buffer? 1. Body chemicals that prevent sharp changes in pH so keep solution neutral 2. Help to control pH in blood, digestive tract, etc. to maintain homeostasis

14. Your stomach juices measure 2 on the pH scale, it is a(n) ___ solution. • a. acidic b. basic c. neutral • The ___ property of water helps in the formation of soil. • a. capillary action b. expansion during freezing c. evaporative cooling • Water has a slight charge on each end. This property makes water a great solvent. This property is called • Polarity b. Capillary action c. Frost wedging • 4. Insects can walk on H2O & paper clips are able to float on H2O because of water’s • Surface tension from hydrogen bonds • Cohesion with other molecules • Adhesion with its own water molecules • High specific heat • 5. Trees are able to move water from the roots to the leaves by the property of water known as • Polarity b. Capillary action c. Surface tension • 6. The ___ property of water removes heat helping to cool your skin through sweating. • a. capillary action b. evaporation c. cohesion

15. Match these pictures with their water properties: 1. 6. • Cohesion & adhesion • Capillary action • Evaporative cooling • Surface tension • Expansion during freezing • Polarity- universal solvent 2. 4. 5. 3.