Sexually Transmitted Infections (STIs)
Image credit singleblackmale.org ZIMSEC O Level Combined Science Notes: Sexually Transmitted Infections (STIs)
To access more topics go to the Combined Science Notes page
February 2025
Safety when using chemicals
Safe use of chemicals. Image credit montana.edu ZIMSEC Combined Science Notes: Safety when using chemicals
- Pesticides are almost always harmful to human beings.
- They are graded according to their level of toxicity i.e. how dangerous they are to humans.
- There are no safe pesticides all are […]
Inhaled vs Exhaled air experiment: Method 2
Lime water is used to test for carbon dioxide. Image weebly.com ZIMSEC O Level Combined Science Notes: Inhaled vs Exhaled air experiment: Method 1
Aim: Test to compare the composition of exhaled and inhaled air.
Materials: Limewater (to test for the presence […]
Food types and their importance
Different types of food have different functions. Image credit healthydietadvisior.com ZIMSEC O Level Combined Science Notes: Food types and their importance
- Carbohydrates-these are energy-rich foods that are largely made up of starch and sugars. They are easily broken down in the […]
Experiment: Growing plants using the vegetative reproduction method
Growing mulberry cuttings. Image credit wordpress.com ZIMSEC O Level Combined Science Notes: Reproduction in plants: Growing plants using the vegetative reproduction method
Materials; trays of soil/sand or prepared garden beds, plant cuttings of sugar cane, mulberry, sweet potato cuttings etc
Method ![Plant [...]
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SeedCo trial fields are used for breeding seeds. Image credit Experiment: The heating curve of water
The heating curve of water. Image credit wordpress.com ZIMSEC O Level Combined Science Notes: Experiment: The heating curve of water
Materials: beaker, crushed ice, thermoter, burner, clock/watch with a stop watch function
Method
- Half fill a beaker with crushed ice
- Record the temperature of the ice
- Place […]
Properties of Nonmetals vs metals
Common metal objects. Image credit blogspot.com ZIMSEC O Level Combined Science Notes: Experiment: Properties of Metals and Non-Metals
- Elements can be divided into two groups:
- Metals and Non-metals
- Examples of metals are: copper, zinc, iron, gold, silver, chrome, lead and tin
- Almost all metals have certain properties that makes them […]
Differences between reduction and oxidation
ZIMSEC O Level Combined Science Notes: Differences between reduction and oxidation
- There are differences between oxidation and reduction
- The table below shows the differences between oxidation and reduction:
- Often reduction and oxidation occur in conjunction
- That is at the same time and during the same reaction
- For example:
- \text{ammonia+oxygen}\rightarrow\text{water+nitrogen dioxide}
- Nitrogen gains oxygen and losses hydrogen […]
Experiment: The effects of a catalyst on the rate of a reaction
Copper (II) can be used as a catalyst. Image credit chemistry-reference.com ZIMSEC O Level Combined Science Notes: Experiment: The effects of a catalyst on the rate of a reaction
Aim: To investigate the effects of a catalyst on a reaction using […]